Flow restrictors are utilized in hydraulic and pneumatic systems to provide predetermined localized resistances to unidirectional and bi-directional fluid flow. Generally, a flow restrictor includes a flowbody, a flow path through the flowbody, and at least one restricted orifice through which the flow path extends. In certain cases, the flow restrictor may also include one or more screens positioned in the flow path upstream of the restricted orifice. For example, a flow restrictor might include a single screen positioned upstream of the restricted orifice in unidirectional flow applications. More commonly, however, two screens are installed on opposing sides of the restricted orifice such that one screen is positioned upstream of the orifice regardless of the flow direction through the restrictor at any particular point in time. Traditionally, a flow restrictor screen assumes the form of a shaped wall or body having perforations therethrough. The perforations are sized to permit the low resistance passage of fluid, while preventing fluid-entrained solid contaminants from reaching and potentially occluding the restricted orifice. Flow restrictor screens are often fabricated as discrete parts or pieces, which are affixed to the flowbody during an assembly process. For example, in one common approach, flow restrictor screens are fabricated from metal sheets, which are perforated, singulated, formed into dome-like shapes, and then secured to the flowbody by brazing.
While relatively straightforward to fabricate, existing flow restrictor designs remain limited in several respects. Conventional flow restrictors are often somewhat costly to manufacture and, in the aggregate, can add non-trivial cost to a pneumatic or hydraulic system containing several flow restrictors distributed throughout the system. Conventional flow restrictors often provide varying levels of flow resistance depending upon the direction of fluid flow through the flowbody, which may be undesirable in certain bidirectional flow applications. Further, in the case of flow restrictors containing prefabricated screens, the screen perforations may be partially covered or blocked by surrounding infrastructure when the screens are installed within the restrictor flowbody. As a result, a certain amount of the flow area through the screen may be non-utilized and, in essence, wasted. It may be possible to compensate for this non-utilized flow area by enlarging the screen perforations or, perhaps, by increasing screen dimensions to accommodate a higher perforation count. Such solutions are less than ideal, however, and may increase the overall size, cost, and weight of the flow restrictor; or can detract from the effectiveness of the screens in blocking the passage of smaller particulate contaminants.
There thus exists an ongoing demand for flow restrictors overcoming most, if not all of the aforementioned limitations. Ideally, such flow restrictors would be amenable to production at reduced manufacturing costs and could be fabricated to have relatively lightweight, compact constructions, particularly in axial dimensions. It would also be desirable if, in at least some embodiments, the flow restrictors could provide highly symmetrical resistance to bi-directional fluid flow through the flow restrictor flowbody. Finally, it is still further desirable to provide methods for fabricating flow restrictors having such favorable characteristics. Other desirable features and characteristics of embodiments of the present disclosure will become apparent from the subsequent Detailed Description and the appended Claims, taken in conjunction with the accompanying drawings and the foregoing Background.